Actinorhizal Plants

Actinorhizal plants are a group of angiosperms characterized by their ability to form a symbiosis with the nitrogen fixing actinobacteria Frankia. 

Actinorhizal plants are dicotyledons distributed among 3 orders, 8 families and 24 genera.  These three orders form a single clade within the Rosids, which is a sister taxon to the other major nitrogen-fixing order, the Fabales.  Not all plants in this clade are actinorhizal, however. 

Order	Family	Genus
Cucurbitales	Coriariaceae	Coriaria
	Datiscaceae	Datisca
Fagales	Betulaceae	Alnus
	Casuarinaceae	Allocasuarina Casuarina Ceuthostoma Gymnostoma
	Myricaceae	Comptonia Myrica
Rosales	Elaegnaceae	Elaeagnus Hipophae Shepherdia
	Rhamnaceae	Colletia Discaria Kentrothamnus Retanilla Talguenea Trevoa Ochetophila Ceanothus
	Rosaceae	Cercocarpus Chamaebatia Cowania Dryas Purshia

 

 

Actinorhizal plants are found on all continents except for Antarctica. Their ability to form nitrogen-fixing nodules confers a selective advantage in poor soils. Most actinorhizal plants are therefore pioneer species that colonize young soils where available nitrogen is scarce. 

Other nitrogen fixing families include Trema ( Parasponia ), a tropical genus in the family Cannabaceae, which are able to interact with Rhizobia.

 

 

 

Gymnostoma sumatranum - Rhu Bukit

Synonym - Casuarina sumatrana.. .

Its native to tropical Asia, found in Malesia-Sumatra region. In Malaysia, it is known as Rhu Bukit. In Sarawak it is a protected species. It is official tree of Kota Kinabalu City Hall of Sabah.. .

Gymnostoma sumatranumis a family of Casuarinaceae, of order Fagales. Casuarinaceae consist of 3 or 4 genera and approximately 70 species of trees and shrubs native to the Old World tropics, Australia and the Pacific Island. At one time, all the species were places in the genus Casuarina, but are now split among Allcasuarina, Casuarina, Ceuthostoma and Gymnostoma.

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Description

A moderately large tree, capable to grow up to 30 meter in heights. Twigs are evergreen, drooping equisetoid. Foliage is of multiple ronded umbrella shaped crowns. The roots have nitrogen fixing nodules that contain the soil actinomycetes Frankia. Stems are angular or tetrahedral in cross section. Female inflorescences are borne terminally . .

Propogation

G. sumatranum is propagated by seeds. Requires a well-drained medium. Germination in 30-90 days.

Propagation by rooting stem shows about 60 – 70 % of success with mature softwood stem cuttings. Rooted cuttings inoculated with Frankia were easily transplanted and established in field conditions with very low (about 3%) mortality. ⁽¹⁾. .

Economics

Its widely use as ornamental trees.

Produce superior quality charcoal in Sarawak. Annual commercial production is about 34,000 tons (weight) of firewood and 4,000 tons of charcoal. ⁽³⁾ . .

Reference

1.Goh C.J. et al, A Simple and Efficient Method of Clonal Propagation of Casuarina sumatrana, Plant Growh Regulation 17:115-120, 1995 (http://www.springerlink.com/content/t725m458205j1074/ )
2. Wikipedia ( http://en.wikipedia.org/wiki/Gymnostoma_sumatranum )
3. Innovations in Tropical Reforestation Casuarinas, nitrogen-fixing trees for adverse sites (http://nzdl.sadl.uleth.ca/cgi-bin/library.cgi?e=d-00000-00---off-0hdl--00-0----0-10-0---0---0direct-10---4-------0-1l--11-en-50---20-about---00-0-1-00-0-0-11-1-0utfZz-8-00&a=d&cl=CL2.18.5&d=HASH010c345e11867f606d9a3478.11)

Casuarina equisetifolia - Rhu Pantai

Synonym : Casuarina litorea

Common names : Casuarina, Australian pine, beach she-oak, beef wood-tree, whistling pine

Etymology

Casuarina is from the Malay word ‘kasuari’, an allusion to the twigs of cassowary bird.

equisetifolia is derived from the Latin ‘equinus’, pertaining to horses, and ‘folium’, a leaf, in reference to the fine, drooping twigs, which are reminiscent of coarse horse hair.

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Natural Habitat & Origin

Sandy coasts of subtropical & tropical ( between 12-31.5°s and 18-22°N ) - Australasia, SE.Asia, islands of the western Pacific Ocean, possible Madagascar.

Classification

Magnoliophyta Magnoliopsida Fagales Casuarinaceae

Description

Evergreen tree with capable to grow up to 20 meters in height.

Crown shape initially conical but tends to flatten with age.

Trunk straight, cylindrical, usually branchless for up to 10m, up to 100cm in diameter. Bark reddish brown colour, rough, brittle, peeling.

Branchlets are deciduous, dropping, needlelike, terete but with prominent angular ribs, 23 – 38 cm x 0.5 – 1 mm, greyish-green.

Flowers unisexual, perianth absent. Monoecious. Pollination by wind.

Male flowers in terminal, simple, elongated spike, 7-40mm long, in whorls, single stamen.

Female inflorescence on a short lateral branchlet, cylindrical, cone-shaped or globose.

Infructescence woody, conelike.

Fruit grey or yellow-grown winged nut (samara).

Seed solitary.

Propagation & Cultivation

Propagation by seeds; cutting from branclests, treated with IBA/IAA/NAA; air-layering is practice, but too costly for large scale operation.

Inoculation with pure strains of Frakia prior to transplanting to field.

Planting density of 2,500stem/ha. Harvested at 10^th – 15^th years.

May plant up to 8,000-10,000 stems/ha for firewood. Harvested at 4^th – 5^th years. Yield 10 – 20 MT/ha/year.

Economic Importance

Firewood : Calorific value 500kcal/kg. Highly regarded wood, ignites readily even when green. Regarded “the best firewood in the world”.

Charcoal : Calorific value 7000kcal/kg .

Paper : Wood to produce paper pulp using neutral sulphate and semi-chemical process.

Timber : Heavy hardwood. Density 900-100kg/m³. Used as house post, rafters, electtic poles, tool handles, oars, wagon wheels, etc.

Folk medicine : Root extrcts are used for treating dysentry, diarrhea, stomach ache. Twigs are used for treating swelling. Powdered bark is used for treating pimples.

Erosion control : planted along coastlines, estuaries, riverbanks, waterways.

Horticulture : Landscape, bongsai.

Weed : Reported to be an invasive weed in Hawaii, the Bahamas, Florida, Nauru.

Others : Tannin, boat making, wind breaker, living fences, nitrogen-fixing.